Electronic systems typically use a power supply to convert alternating current (AC) voltage to direct current (DC) voltage. The AC voltage may be 120 VAC and the DC voltage is whatever is needed by the electronic system for proper operation (e.g., 3.3 VDC, 5 VDC, etc.). Some types of electronic systems (e.g., server computers) use more than one power supply for redundancy so that if one power supply fails, another power supply can provide the needed current to the load. In redundantly configured power supplies, the output voltage from the supplies may be connected together and, from that point, a single conductor is routed to the load to carry the DC voltage. That single conductor may comprise a wire or a trace on a circuit board.
Some power supplies may have over-current output protection. That is, the power supply's output will automatically shut off if the output current drawn by the load exceeds a particular threshold. When both supplies in a dual, redundant power supply configuration are operating normally, each supply, all else being equal, supplies one-half of the current needed by the load. However, because each supply may have to supply all of the current needed by the load upon a failure of the other supply, each supply typically has its over-current threshold set at approximately the maximum current needs of the load.
With both supplies operating correctly, in general neither supply will be forced to deliver current at or near the over-current threshold, unless the load experiences a short-circuit. In that case, the current demand on each supply will increase until the current output from each supply reaches the over-current threshold. At that point, the supplies will shut down. Because the aforementioned scenario could happen, the power conductor to the load that carries all of the combined current produced by the single power supplies must be large enough to carry the combined maximum current from all supplies. Such a conductor may be considerably large and thus undesirable.